Wireless local area networks (WLAN) and real time location systems (RTLS) are becoming more commonplace as the use of portable computers, such as “laptop,” “notebook,” and “pen” computers become increasingly common in office environments and other locations. Examples of real time location systems and the circuitry and algorithms used in such real time location systems are described in U.S. Pat. Nos. 5,920,287; 5,995,046; 6,121,926; and 6,127,976, the disclosures which are hereby incorporated by reference in their entirety. Examples of a real time location system that is operative with a wireless local area network are disclosed in commonly assigned copending utility patent application Ser. No. 09/997,282, filed Nov. 29, 2001, and copending utility patent application Ser. No. 10/023,481, entitled “Wireless Local Area Network System with Mobile Access Point Station Determination,” filed Dec. 17, 2001, the disclosures which are hereby incorporated by reference in their entirety.
In many of these types of systems, the amount of signal interference continues to increase to the point that some of the communication systems lose their effectiveness. There are some techniques that mitigate these effects, such as the use of spread spectrum and altenna diversity, as disclosed in the above identified patents and applications. In any event, if the wireless and real time location networks increase in number, the spread spectrum and diversity techniques are not sufficiently effective.
In the wireless environment, such as a wireless local area network and real time location system, the environment is crowded with a number of communication signals and other interfering signals that occupy the same frequency bands or channels. Also, the environment is typically contaminated by multipath reflections from both the desired communication signal emanating from a desired transmitter, such as a mobile device, TAG, or mobile access point, and interfering signals emanating from interfering sources, such as other networks and antennae. Reflections can occur by wave reflecting services, including walls, buildings, other antenna, natural earth landmarks and other reflecting sources known to those skilled in the art.